Spring-biased tip assembly

ABSTRACT

A maneuverable distal apparatus includes a temperature-activated memory element moving in a first direction to assume a predetermined shape when heated to a predetermined temperature and control means for selectively heating the memory element so that the memory element is moved in the first direction. A spring is provided for yieldably urging the memory element in a second direction away from the first direction upon cooling of the memory element to a temperature less than the predetermined temperature so that the memory element is moved to assume a shape other than the predetermined shape.

BACKGROUND AND SUMMARY OF THE INVENTION

This application is a continuation of application Ser. No. 07/282,318filed Dec. 8, 1988, now abandoned, which is a continuation ofapplication Ser. No. 07/103,926, filed Oct. 2, 1987, now abandoned,which is a continuation-in-part of copending application Ser. No.06/870,926, filed June 5, 1986, now U.S. Pat. No. 4,758,222 which is acontinuation-in-part of copending application Ser. No. 06/728,634 filedMay 3, 1985, now U.S. Pat. No. 4,601,705, which is acontinuation-in-part of application Ser. No. 06/547,402 filed Oct. 31,1983, now U.S. Pat. No. 4,543,090.

The present invention relates to guide apparatus, probes, and the like,and particularly to guide apparatus that are steerable through bodycavities and aimable at obstructions, organs, or tissue within the bodyfrom a position external to the body. More particularly, the presentinvention relates to maneuverable guide apparatus including spring meansfor biasing a temperature-activated memory element to alter the shape ofthe memory element upon cooling of the memory element to a temperaturebelow its martensitic transformation temperature.

Some attempts have been made in the past to provide catheters havingdistal ends which, when inserted into a body, are manipulatable toadvance the catheter through body cavities. See for example, U.S. Pat.Nos. 3,674,014 and 3,773,034. The catheter disclosed in Pat. Nos.3,674,014 includes permanent magnets and employs a magnetic field tobend the distal end of the catheter. The catheter disclosed in Pat. No.3,773,034 includes fluid conduits and employs a fluid to bend the distalend of the catheter. Other controlled devices are disclosed in U.S. Pat.No. 3,605,725 and 4,176,662. However, these prior devices are quitedifficult to control and manipulate.

Some work has previously been done to produce a catheter which isreadily insertable while being effectively anchorable in a body cavity.See, for example, U.S. Pat. Nos. 3,729,008 and 3,890,977.

In U.S. Pat. No. 3,890,977 to Wilson, the distal end of the catheter isformed into a desired shape by using a material exhibiting mechanicalmemory that is triggered by heat. By heating the mechanical memorymaterial, the distal end of the catheter is shaped to anchor thecatheter within the body. However, the change of the shape or othermovement of the distal end in these prior devices is limited to a singledirection. Once the memory material has been heated causing the distalend to move in said single direction to assume its characteristicanchoring shape, it becomes necessary to deform the distal end manuallyat a temperature below the transition temperature of the mechanicalmemory material in order to change the shape of the distal end. The needfor manual manipulation of a catheter once it is inserted into a bodylimits the steerability and aimability of the catheter.

Other devices are known for guiding a catheter to a particular locationwithin the body. See for example U.S. Pat. No. 3,043,309.

One object of the present invention is to provide a steerable guideapparatus, probe, and the like which is easy to operate and steerable ina plurality of different directions within the body.

Another object of the present invention is to provide an aimable guideapparatus, probe, and the like which is easy to operate and which can beaimed at obstructions, organs, or tissues in a plurality of differentdirections within the body.

Yet another object of the present invention is to provide a guideapparatus, probe, and the like of improved maneuverability having meansfor slidably coupling each of a plurality of temperature-activatedmemory elements to a core member so that each memory element ispermitted to slip in relation to the adjacent core member when at leastone of the memory elements is heated to assume a predetermined"memorized" shape.

Another object of the present invention is to provide a steerable andaimable guide apparatus, probe, and the like of very simple designhaving only one temperature-activated memory element that is movable toa predetermined shape using remote controls to steer and aim the guideapparatus and yet is automatically returnable to an initial shapewithout manual manipulation by an operator.

Still another object of the present invention is to provide a highlymaneuverable guide apparatus, probe, and the like having at least oneresilient element for biasing the distal end of the guide apparatus toassume an initial shape and a separate temperature-activated memoryelement that is movable under heat to bend the distal end of the guideapparatus to a multiplicity of shapes other than the initial shape.

Another object of the present invention is to provide a steerable andaimable guide apparatus, probe, and the like of simple constructionwherein a memory element is employed to deflect a guide wire made ofspring material.

Yet another object of the present invention is to provide a steerableand aimable guide apparatus, probe, and the like wherein the guide wireis made of a resilient shape-memory material.

Still another object of the present invention is to provide a steerableand aimable guide apparatus, probe, and the like wherein atemperature-activated memory element made of a shape-memory alloy andemployed to deflect a guide wire made of spring material is coupled tothe guide wire to apply an axial compression pulling force to the guidewire as the length of the memory element is shortened upon being heatedto a predetermined temperature in accordance with a thermal property ofthe shape-memory alloy so that the guide wire is "pulled" along its axisby the memory element to assume a different shape.

According to the present invention, a maneuverable distal apparatusincludes a temperature-activated memory element moving in a firstdirection to assume a predetermined shape when heated to a predeterminedtemperature and spring means for yieldably urging the memory element ina second direction away from the first direction upon cooling of thememory element to a temperature less than the predetermined temperatureso that the memory element is moved to assume a shape other than thepredetermined shape. The apparatus also includes insulation means forpreventing unwanted electrically conductive contact between the memoryelement and the spring means and control means for selectively heatingthe memory element so that the memory element is moved in the firstdirection.

In preferred embodiments, the spring means is an elongated coil springformed to include a longitudinal cavity and the memory element ispositioned in the longitudinal cavity. The insulation means includes atubular sleeve positioned in the longitudinal cavity and the memoryelement is positioned in the tubular sleeve. An end cap is coupled to adistal end of the elongated coil spring and the insulation meansincludes means for preventing electrically conductive contact betweenthe memory element and the end cap.

The control means includes power supply means, first electrical leadmeans for coupling the power supply means and the spring means inelectrical communication, and second electrical lead means for couplingthe power supply means and the memory element in electricalcommunication. Circuit means interconnecting the spring means and thememory element is provided for establishing an electrical circuitelectrically connecting the spring means, the memory element, and thecontrol means in series.

In another preferred embodiment, the guide wire is a tubular coiledspring made of a resilient shape-memory alloy. Control means is providedfor selectively heating the tubular coiled spring to at least apredetermined temperature so that the tubular coiled spring moves fromits initial shape to assume its predetermined shape. The tubular coiledspring returns toward its initial shape upon being cooled to atemperature less than the predetermined temperature.

In yet another embodiment, the memory element is disposed inside ahollow axially compressible guide wire made of spring material andanchored at its opposite ends to spaced-apart distal and proximalportions of the guide wire. The "double-anchored" memory elementshortens in length in accordance with due to a characteristic thermalproperty of the shape-memory alloy comprising the memory element uponbeing heated to a predetermined temperature. Such shortening acts toapply an axial compression load to the axially compressible guide wire,thereby effectively "pulling" the guide wire to assume a differentshape. The guide wire returns toward its initial shape upon cooling ofthe memory element to a temperature less than the predeterminedtemperature due, in part, to spring characteristics of the guide wire.One notable advantage of this double-anchored feature is that the sizeand mass of the memory element can be reduced significantly incomparison to other embodiments since less force is required to pull theguide wire to a different shape than to push the guide wire to the sameshape. It will be understood that "pulling" refers generally to axialcompression loading or the like of the guide wire, while "pushing"refers generally to transverse shear loading or the like of the guidewire.

Additional objects, features, and advantages of the invention willbecome apparent to those skilled in the art upon consideration of thefollowing detailed description of preferred embodiments exemplifying thebest mode of carrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the accompanying figuresin which:

FIG. 1 is a perspective view of a steerable and aimable guide apparatusembodying the present invention;

FIG. 2 is a longitudinal cross-sectional view, partly broken away, of abody Cavity and the distal end of the guide apparatus shown in FIG. 1;

FIG. 3 is a perspective view of an embodiment of a temperature-activatedmemory element employed in the guide apparatus showing its differentshapes;

FIG. 4 is a transverse cross-sectional view of the distal end of theguide apparatus embodying the present invention taken generally alongsection lines 4--4 in FIG. 2;

FIG. 5 is a longitudinal cross-sectional view of a body cavity showingthe aimable feature of a guide apparatus embodying the presentinvention;

FIG. 6 is a transverse cross-sectional view of the embodiment of theguide apparatus shown in FIG. 5 taken generally along section lines 6--6of FIG. 5;

FIG. 7 is a perspective view of an embodiment of a plurality oftemperature-activated memory elements employed in the distal end of theguide apparatus to deflect or move the distal end for steering andaiming thereof;

FIG. 8 is an exploded view of another embodiment of the presentinvention;

FIG. 9 is a longitudinal sectional view, partly broken away, showing theembodiment of FIG. 8 in its relaxed position and taken generally alongsection lines 9--9 of FIG. 8;

FIG. 10 is a view, partly broken away, of the embodiment of FIG. 9rotated 90° about its longitudinal axis;

FIG. 11 is a longitudinal sectional view, partly broken away, showingthe embodiment of FIG. 8 in a deflected position;

FIG. 12 is a longitudinal sectional view of yet another embodiment ofthe present invention, partly broken away, showing the distal end of aguide apparatus in a relaxed position;

FIG. 13 is a view of the embodiment of FIG. 12, partly broken away,showing the distal end of the guide apparatus in a partially deflectedposition;

FIG. 14 is a view of the embodiment of FIG. 12, partly broken away,showing the distal end of the guide apparatus in a fully deflectedposition;

FIG. 15 is a longitudinal sectional view of another embodiment of thepresent invention showing a temperature-activated memory elementpositioned within a coiled spring;

FIG. 16 is a longitudinal sectional view of yet another embodiment ofthe present invention;

FIG. 17 is a longitudinal sectional view of still another embodiment ofthe present invention showing a type of circuit means different thanthat shown in FIGS. 15 and 16;

FIG. 18 is a transverse sectional view, taken generally along lines18--18 of FIG. 17, showing rotation of a guide wire in a clockwisedirection about its longitudinal axis in response to heating thetemperature-activated memory element inside above its transitiontemperature;

FIG. 19 is a longitudinal sectional view of yet another embodiment ofthe present invention having a temperature-activated memory elementconfigured to provide its own spring return means;

FIG. 20 is a longitudinal sectional view of still another embodiment ofthe present invention having a double-anchored temperature-activatedmemory element arranged to apply pulling force to its companion springreturn means during movement of the memory element to assume apredetermined shape under thermal loading; and

FIG. 21 is a longitudinal sectional view of yet another embodiment ofthe present invention having a double-anchored temperature-activatedmemory element coupled directly to a current source.

DETAILED DESCRIPTION OF THE DRAWINGS

A catheter 10 embodying the present invention is shown generally inFIG. 1. Catheter 10 includes an elongated tubular member 12 having aproximal end 14 and a steerable and aimable distal end 16. In theillustrative embodiment, the tubular member 12 is formed of plastic,TEFLON, or cross-linked kynar or polyethylene. As will become apparentin the description of catheter 10, it is desirable that tubular member12 be formed of a material that is flexible, that can withstand heat,and which provides electrical insulation.

As best shown in FIG. 2, the tubular member 12 can have a lumen 18 forthe passage of fluid from the proximal end 14 to the distal end 16 andvice versa. Typically, the tubular member 12 includes one or more holesor openings 19 through which fluids are either injected into or drainedfrom a body cavity. Some cannulae may have an open distal end 16 forinsertion and withdrawal of medical instruments.

As shown in FIGS. 2 and 3, a plurality of temperature-activated memoryelements 20 are incorporated into the distal end 16 of the tubularmember 12. It may be desirable to isolate the memory elements 20 fromthe body cavity. The temperature-activated memory elements 20 preferablyexhibit a memory characteristic in response to temperature changes. Theelements 20 may be wires or flat strips such as shown in FIG. 3. In theillustrative embodiment, the temperature-activated memory elements 20are formed of a mechanical memory metal such as a nickel titanium alloy.While a nickel titanium alloy is desirable, other metal elements havinga memory characteristic related to temperature could be used withoutdeparting from the scope of the invention. Such metal elements shouldhave a high resistance to electric current so that heat is produced whencurrent is passed therethrough.

As shown in FIG. 3, the elements 20 have a body portion 22 and a tipportion 24. Each element 20 has a first or preset shape represented bythe broken lines in FIG. 3 and a second shape represented by the solidlines in FIG. 3. Illustratively, the preset shape is an arcuate shape,and the second shape is a straight shape. It will be appreciated thatthe preset shape could be any shape.

Each temperature-activated memory element 20 is originally annealed intoits preset shape (represented by the broken lines in FIG. 3). Memoryelements 20 are cooled and straightened to their second shape(represented by the solid lines in FIG. 3) before incorporation into thedistal end 16 of the tubular member 12. When the elements 20 are againheated to a predetermined transitional temperature they return to theirpreset shape. By applying an opposing force to an element 20 that hasmoved to assume its preset shape it can be moved to its second shape(represented by the solid lines in FIG. 3). In the illustrativeembodiment, the predetermined transitional temperature is anytemperature above body temperature. For example, the predeterminedtransitional temperature may be in the range of 100 to 150° F.

The memory elements 20 can either be directly incorporated into thedistal end 16 of the tubular member 12 or can be carried on anelectrically insulative core 50. As will be discussed later, each memoryelement 20 must be coupled to at least one other memory element 20 sothat when one of the memory elements is heated it applies a force tomove the other memory element 20.

The catheter 10 further includes an electronic control system 30 forcontrolling current flow to vary the temperature of eachtemperature-activated memory element 20 from a position external to thebody so as to deflect the distal end 16 of the tubular member 12 in aplurality of different directions corresponding to the preset shapes ofthe elements 20. The control system 30 includes a power supply source 32which may be either AC or DC. The system 30 also includes a controldevice 34 which, in the illustrative embodiment, is similar to a"joystick" control, tactile membrane switch, or ball controller. It willbe appreciated that various types of control devices 34 may be employedwithout departing from the scope of the present invention.

The power supply source 32 is coupled through control device 34 to thetubular member 12 by cable 36 and a coupling device 38. Further, thetemperature-activated memory elements 20 are electrically connected tothe control device 34 through cable 36 and coupling 38 by electricalwires 40 which are attached to the body portions 22 of memory elements20 by conventional means 42 such as soldering or crimping. Return orground wires 44 are attached to the tip portions 24 of memory elements20 by conventional means such as soldering or crimping 46. Return orground wires 44 may be combined into a single ground cable 48 as shownin FIG. 2.

In the embodiment illustrated in FIG. 2, the temperature-activatedmemory elements 20 are carried on the exterior of the core 50 and groundwire 48 runs through the interior of the core 50. Core 50 couples eachmemory element 20 to at least one other memory element 20 so that when amemory element 20 moves to assume its preset shape in response to heatit applies a force to move the other memory element 20 coupled thereto.In preferred embodiments, the core 50 is a tube formed of urethanehaving a wall thickness of about 0.005 inch. In other embodiments, thecore 50 may be a fiber optics bundle, electrical wire, microinstrumentation, or any other suitable member. Other mountingarrangements could be used for incorporating the memory elements 20 intothe distal end 16 of the tubular member 12 without departing from thescope of the present invention.

In operation, the distal end 16 of the tubular member 12 is insertedinto a body cavity 60 such as a blood vessel while memory elements 20are straight and at a temperature below the transitional temperature. Atthis stage, each memory element 20 is in its second shape for readyinsertion of the distal end 16 into the body cavity 60. The tubularmember 12 is pushed through cavity 60 until it reaches a desired branch62 or 64 extending from the cavity 60. Control device 34 is manipulatedto apply an electrical voltage or current to one or more of the memoryelements 20. Because of the high resistance of memory elements 20, heatis generated. When a memory element is heated to its predeterminedtransitional temperature (i.e., a predetermined temperature above bodytemperature) the memory element 20 moves to assume its preset shape (asshown by the broken lines in FIG. 3), thereby deflecting or moving thedistal end 16 of tubular member 12 into one of the desired branchcavities 62 or 64. Once the distal end 16 is in the branch 62 or 64,power can be removed from the memory element 20 to allow it to cool.While the memory element 20 is at a temperature above its predeterminedtransitional temperature it remains relatively stiff in its presetshape. When the memory element 20 cools to a temperature below itspredetermined transitional temperature it becomes soft or pliable in itspreset shape. After cooling, a voltage or current is applied to anothermemory element 20 coupled to the cooled memory element 20 still in itspreset shape. When the other memory element 20 reaches its predeterminedtransitional temperature, it begins to move to assume its preset shapeand in doing so applies a force to the memory element 20 coupled theretoto move it to its second shape (as shown by the solid lines in FIG. 3).The catheter tubular member 12 can continue to be pushed through thebranch 62 or 64 until it is again desirable to turn or bend the catheter10.

As illustrated in FIG. 4, four temperature-activated memory elements 20may be carried on the exterior of core 50. In the illustrativeembodiment, pairs of the memory elements 20 are shown diametricallyopposed to each other so that opposed elements 20 apply forces to eachother when they are heated. Thus, the distal end 16 may be deflected inat least four different directions by applying an electrical current orvoltage to one of the memory elements 20. It will be appreciated thatmore or less than four memory elements 20 may be utilized withoutdeparting from the scope of the present invention. However, it should benoted that at least two memory elements 20 are required. Further, it maybe desirable to apply an electrical voltage or current to more than oneof the memory elements 20 simultaneously to increase the number ofdirections in which the distal end 16 of the tubular member 12 may bedeflected. The control system 30 may include means for regulating theapplication of current or voltage applied to the memory elements 20 toallow virtually an unlimited number of directions in which the distalend 16 may be deflected for the purpose of steering the catheter tubularmember 10 through body cavities. It will be appreciated that a largenumber of wire memory elements could be incorporated into the distal end16 and a voltage or current applied to one or more of the wires todeflect the distal end 16 in a desired direction.

Another application for a catheter 70 embodying the present invention isshown in FIGS. 5 and 6. Reference numerals from FIGS. 1-4 have beenapplied to the catheter 70 shown in FIGS. 5 and 6 where the same orsimilar parts are being used. Catheter 70 includes a tubular member 72having a distal end 76. The distal end 76 includes a plurality oftemperature-activated memory elements 20 of the type previouslydescribed. The same or similar control system may be employed inconnection with the catheter 70 in a body cavity 80 for the purpose ofaiming the distal end 76 at an obstruction, organ, or tissue 82 withinthe cavity 80. The catheter 70 may be anchored in the cavity 80 by aballoon 78. Once the catheter 70 is anchored, the distal end 76 is aimedin one of a plurality of directions to establish a course for theinjection of fluid or a laser beam at the organ or tissue 82.

As shown in FIG. 6, a core 90 formed of insulative material passesthrough tubular member 72. Memory elements 20 are carried on the core 90between the core 90 and the tubular member 72. Core 90 serves to coupleeach memory element 20 to at least one other memory element 20 in themanner and for the purpose previously described. The hollow core 90 mayinclude a first tube 92 for carrying a fluid from the proximal end ofthe catheter 70 to the distal end 76. A return tube 94 may be includedfor extracting fluid. It will be appreciated that either passage 92 or94 may be used for inserting a medical instrument into the cavity 80.Core 90 may also include a transparent member 95 providing a lens forobserving the obstruction, organ, or tissue 82 and a bundle offiber-optic lines 96 for transmitting light or a laser beam to thedistal end 76. Thus, in the embodiment illustrated in FIGS. 5 and 6,catheter 70 has a distal end 76 which is aimable in a plurality ofdirections in accordance with the present invention for the purpose ofestablishing a course for the injection of fluid, light, or a laser beamat an obstruction, organ, or tissue 82.

Another embodiment of an arrangement for the memory elements 20 is shownin FIG. 7. The memory element arrangement 100 includes a plurality ofmemory elements 20 coupled at their distal ends 24 by a thermally andelectrically insulative ring 102. Various materials, such as plastic,may be used to construct the ring 102. Ground wires from each memoryelement 20 are channeled through a common ground wire conduit 44. Ring102 serves to couple the memory elements 20 to each other and performs afunction similar to cores 50 and 90. This arrangement facilitates themounting of the memory elements 20 in the distal end 16, 76 of thecatheters 10, 70, respectively.

Yet another embodiment of the present invention is shown in FIGS. 8-11.Reference numerals from FIGS. 1-4 have been applied to a catheter 110shown in FIGS. 8-11 where the same or similar parts are being used.Catheter 110 includes a tubular member 12, a pair oftemperature-activated memory elements 20a and 20b, and a core 50 of thetypes described above. Memory elements 20a and 20b may be flat as shownin FIGS. 8-11 or in some applications may be wires, particularly wheremore than two memory elements are employed. The catheter 110 furtherincludes a sleeve 112 for slidably coupling each memory element 20a,b tothe core member 50 so that each memory element 20a,b is permitted toslip in relation to the adjacent core member 50 when at least one of thememory elements 20a,b moves to assume its predetermined shape. Thesleeve 112 also interconnects one memory element to another memoryelement so that when one memory element moves in a first direction toassume its preset shape a force is applied to move the other memoryelement in the first direction and vice versa.

Desirably, the sleeve 112 is a resilient tubular jacket for embracingelastically the core member 50 and the memory elements 20a,b to providea slip interface therebetween. The sleeve 112 include an axially innerportion 113 for the reception of a distal end of the core 50 and the tipportions 24 of each memory element and an axially outer portion 114 forthe reception of a forward tip portion of the core. Thus, each memoryelement received within the sleeve 112 simultaneously is retainable in acore-guiding position as shown in FIGS. 9-11 and is movable with thesleeve 112 to deflect the distal end of the core 50 to a selectedposition (e.g. the deflected position illustrated in FIG. 11).

The sleeve 112 includes an inner wall 115 defining a slip chamber 116 inwhich each memory element is able to slip in relation to the core member50 during selective heating of at least one of the memory elements 20.In preferred embodiments, the sleeve 112 is formed of thin MYLARmaterial having a thickness of about 0.001 inch. Any other similarmaterial that has a low coefficient of friction and is not generallysusceptible to deformation under heat would be suitable.

As shown best in FIGS. 8 and 9, the core 50 includes a distal end 118having a forward tip portion 120. Installation of the sleeve 112operates to position the forward tip portion 24 of each memory element20a,b in close proximity to the distal end 118 of the core 50. The firstand second memory elements 20a,b are positioned on opposite sides of thecore 50 in spaced relation as shown in FIGS. 8, 9, and 11 so that thecore 50 is intermediate the two memory elements. Thus, the forward tipportion 24 of each memory element is retained in its core-guidingposition by sleeve 112. In addition, the remaining body portion 22 ofeach memory element is retained in its core-guiding position by means ofa wrap.

The memory element retaining wrap is desirably a continuous filament 122as illustrated in FIGS. 8-11. For example, a nylon filament having a0.002 inch diameter would be satisfactory. The filament wrap 122 couplesat least a segment of the body portion 22 of each memory element 20a,bto the core 50 so that the body remaining portion segment is permittedto slip in relation to the adjacent core 50 when at least one of thememory elements 20a,b moves to assume its preset shape. Desirably, thefilament wrap 122 embraces a radially outwardly facing surface 124 ofeach of the memory elements in sufficiently tight relation to retain thememory elements in their coupled position while permitting relativeslipping movement between each coupled memory element and the core 50.As shown in FIGS. 8 and 10, the continuous filament 122 defines aplurality of winding bunches 126 disposed along the length of the Core50 in spaced-apart relation so that each winding in a winding bunch 126can move along the core in relation to one another in the spaces 128therebetween during deflection or bending of the distal end 16 of thetubular member 12. Illustratively, each spaced winding bunch 126includes three windings as shown in FIGS. 8 and 10.

In the embodiment illustrated in FIGS. 8-11, the temperature-activatedmemory elements 20a,b are electrically connected to the control device34 by wire 130 of rectangular cross-section. The remainder ofrectangular wire 130 is mounted along the side edge 132 of the remainingportion 22 of each memory element 20. Return or ground wire 134 is alsoof rectangular cross-section and mounted along another side edge 136 ofeach memory element at a proximal end of the remaining body portion 22of the memory element. Other suitable electrical coupling means areusable to couple the memory elements of the embodiment of FIGS. 8-11 tothe control device 34 without departing from the scope of the presentinvention.

In operation, the sleeve 112 included in the embodiment of FIGS. 8-11provides numerous advantages. One advantage is that maneuverability ofthe catheter 110 is improved due to slippage of each memory element20a,b relative to core 50 in the slip chamber 116 defined by the sleeve112. A certain amount of slippage is desirable to allow relativemovement of the memory elements 20 and the core 50 to improve theflexibility of the catheter. As shown best in FIG. 11, movement of thefirst memory element 20a to assume its predetermined position causes theforward tip portion 24 of the first memory element 20a to move along theexterior surface of the core 50 toward the forward tip portion 120 ofthe core 50 and the forward tip portion 24 of the second memory element20b to move along the exterior surface of the core 50 away from theforward tip portion 120 of the core 50. In other words, the first memoryelement 20b is arcuately shaped when the memory element 20a moves toassume its predetermined shape and vice versa. In particular, the arcdefined by the memory element 20a is smaller than the arc defined by theequidistantly spaced-apart memory element 20b as shown in FIG. 11. Theslippage of memory elements 20a and 20b relative to the forward tipportion 120 of core 50 is shown by the arrows in FIG. 11. Arrow 140represents the positions of the tips 24 before deflection and arrows 142and 144 represent the positions of the tips 24 of elements 20b and 20arespectively when the catheter is deflected.

Still another embodiment of the present invention is shown in FIGS.12-14. Reference numerals from FIGS. 1-4 and 8-11 have been applied to acatheter 210 as shown in FIGS. 12-14 where the same or similar parts arebeing used. Catheter 210 includes a tubular member 12, atemperature-activated memory element 20, and a sleeve 112 of the typesdescribed above.

An electrically insulative hollow core member 240 is provided in theinterior of tubular member 12 for receiving medical instruments, fiberoptics lines, fluid-conducting tubes, or other medical or optical tools.Core member 240 is desirably made of plastics material such as urethane,TEFLON, KYNAR, or polyethylene and has a wall thickness of 0.005-0.010inch (1.27-2.54 mm). In contrast to the core members illustrated inconnection with the embodiments of FIGS. 1-11 that are generallystraight in their relaxed positions, core member 240 is preformed usingknown techniques to assume a curved shape in its relaxed position asshown in FIG. 12.

The catheter 210 further includes a spring 242 positioned on theexterior of curved core member 240 in diametrically opposed relation tomemory element 20. The spring 242 is desirably made of stainless steelor plastics material and has a thickness of 0.010 inch (2.54 mm). Thespring 242 is also preformed using known techniques to assume a curvedshape. As shown in Fig. 12, the radius of curvature of preformed spring242 is less than the radius of curvature of curved core member 240.

Spring 242 effectively serves as a resilient memory element or means andcooperates with core 240 to load memory element 20 with a force thatbends memory element 20 to an initial shape illustrated in FIG. 12. Thespring constant of spring 242 is selected to cause spring 242 to providea predetermined biasing force to bend the distal end of the catheter inone direction as shown in FIG. 12 and also yield under loading providedby the heated memory element 20 to permit the distal end of the catheterto bend in an opposite second direction as shown in FIGS. 13 and 14.

Sleeve 112 slidably couples memory element 20 and preformed spring 242to curved core member 240 so that the memory element 20 and spring 242are permitted to slip in relation to the adjacent core member 240 wheneither of the memory element 20 and the spring 242 move to assume itspreset shape. The sleeve 112 also interconnects memory element 20 tospring 242 so that when the memory element 20 moves in a first direction254 to assume its preset shape a force is applied to move the spring 242in the first direction 254 and vice versa.

In the diagrammatic embodiment illustrated in FIGS. 12-14, thetemperature-activated memory element 20 is electrically connected to acontrol device 234 and a power supply 244 by wires 130, 134, and 246.Control device 234 includes switch means 248 and power control means250. Switch means 248 is operable to decouple the power supply 244 andthe memory element 20 to prevent heating of memory element 20. Powercontrol means 250 is operable to vary the electrical power provided tomemory element 20, thereby regulating the amount of heat applied tomemory element 20. Illustratively, power control means 250 is arheostat. It will be appreciated by those skilled in the art that themanner of controlling the temperature of memory element 20 can beaccomplished using a variety of control systems other than theillustrated system without departing from the scope of the presentinvention.

One exemplary operation sequence of catheter 210 is illustrated in FIGS.12-14. In particular, the relaxed state of the distal end of tubularmember 12 is shown in FIG. 12. The preset Curved shapes of core member240 and spring 242 act to bend the distal end of tubular member 12 indirection 252 as shown in FIG. 12. At this stage, switch means 248 is inits open circuit position, preventing current generated by power supply244 from being applied to heat the memory element 20. Thus, therelatively cool memory element 20 is also bent in direction 252 due tothe interconnection with core member 240 and spring 242 established bysleeve 112 and tubular member 12. Such bending resulting from the presetcurved shapes of core member 240 and spring 242 effectively defines an"initial position" of the memory element 20 and the distal end tubularmember 12.

Steering and aiming of catheter 210 is accomplished by operation ofcontrol device 234 in the following manner. Once switch means 248 ismoved to its closed circuit position shown in FIGS. 13 and 14, theoperator can control the heating and cooling of thetemperature-activated memory element 20 by using power control means250.

Movement of power control means 250 to a first setting illustrativelydepicted in FIG. 13 causes a sufficient amount of power to be applied tomemory element 20 so that the memory element 20 is heated and moves indirection 254 away from its initial curved shape to assume asubstantially straight shape. The steering force generated by suchmovement is transmitted to core member 240 and spring 242 in part viasleeve 112. This steering force is sufficient to overcome opposing"return" forces generated by core member 240 and spring 242.

Continued movement of power control means 250 to another power settingillustratively depicted in FIG. 14 causes still more power to be appliedto memory element 20. This heats memory element 20 to a higher"predetermined" temperature, causing the memory element 20 to continueto move in direction 254 to assume a "predetermined" curved shape.

Return of the catheter 210 to its initial relaxed state shown in FIG. 12is easily accomplished by using control device 234 to lessen the amountof power applied to memory element 20. This step allows memory element20 to cool, thereby permitting preset core member 240 and spring 242 tocooperate to exert a return force on the distal end of the tubularmember 12 and memory element 20. Such a return force acts in direction252 in the absence of a steering force generated by memory element 20,thereby causing catheter 210 to be returned to its relaxed state.

It will be appreciated that a plurality of pairs oftemperature-activated memory elements 20 and springs 242 could bepositioned in the distal end of the catheter to provide a great deal offlexibility in steering and aiming the catheter. However, it will beunderstood that it is possible to steer and aim a catheter provided withonly a single temperature-activated memory element 20 and return spring242 in a multiplicity of radial directions by rotating the catheterabout its central longitudinal axis during heating of memory element 20using control device 234.

Several other embodiments of the present invention are shown in FIGS.15-21. In each of the embodiments illustrated in FIGS. 15-21, a heatabletemperature-activated memory element is positioned within a guide wiremade of spring material. In the embodiment illustrated in FIG. 19, theguide wire is made out of a resilient shape-memory alloy so that theguide wire itself performs both a memory function and a spring returnfunction.

FIGS. 15-21 illustrate preferred embodiments of using atemperature-activated shape-memory alloy to deflect a guide wire or thelike. Although such steerable guide wire assemblies are easily installedin catheters as shown, it will be appreciated that the steerable guidewire concept has much broader application and does not necessarily haveto be inserted within a catheter. In other words, the guide wire itselfcan provide a catheter for insertion into canals, vessels, passageways,or body cavities to permit injection or withdrawal of fluids or to keepa passage open.

One embodiment of a steerable guide wire assembly is illustrated in FIG.15. Memory element 310 is positioned in an interior chamber 312 of guidewire 314. Memory element 310 is oriented to deflect guide wire 314 froman initial position (solid lines) to a deflected position (phantomlines) upon bending movement of memory element 310 to assume apredetermined bent shape (not shown).

Memory element 310 is desirably made of a shape-memory alloy such asnitinol and configured to include a pair of lead-attachment portions316a, b and a shape-memory portion 318. Reference is hereby made to U.S.Pat. No. 4,777,799 to McCoy et. al. entitled "Memory Element" and filedconcurrently herewith, for a description of the construction, function,and operation of portions 316 and 318.

Guide wire 314 is desirably a coil made of TEFLON-coated 304 stainlesssteel spring material. Guide wire 314 includes a proximal portion 320disposed in base 324 and a distal portion 322 to provide an assembly forsteering and aiming the base 324. It will be understood that base 324can be configured to provide a catheter, cannula, or the like forreceiving guide wire 314 or that guide wire 314 can function inaccordance with the present invention on its own as a catheterindependent of any such base means.

A rounded cap 326 is coupled to the distal portion 322 of guide wire 314to provide a smooth probe tip for the assembly. An insulative sleeve 328having a side wall 330 and a top wall 332 is positioned in the interiorchamber 312 of guide wire 314 so that top wall 332 lies in abuttingrelation to cap 326 and side wall 330 lies intermediate guide wire 314and memory element 310. Advantageously, insulative sleeve 328 preventselectrical communication between memory element 310 and each of guidewire 314 and cap 326.

An electrical system is provided for selectively heating memory element310 to a temperature in excess of its transition temperature by varyingthe current passing through memory element 310 so that memory element310 moves to assume a predetermined shape and deflect guide wire 314.Such deflection results from engagement of guide wire 314 by the movingmemory element 310 disposed within interior chamber 312 of guide wire314. Thus, movement of guide wire 314 is induced by moving memoryelement 310 without depending upon a fixed coupling between guide wire314 and memory element 310. The electrical system includes a powersupply 334, first lead means 336 for electrically connecting oneterminal of the power supply 334 to lead-attachment portion 316b, andsecond lead means 338 for electrically connecting another terminal ofpower supply 334 to lead-attachment portion 316a.

Another embodiment of the invention is illustrated in FIG. 16. Referencenumerals from FIG. 15 have been applied to the assembly as shown in FIG.16 where the same or similar parts are being used. In this embodiment,an insulative coating material (not shown) is applied to at least one ofmemory element 310, guide wire 314, and cap 326 in lieu of insulativesleeve 328. Thus, the insulative coating also acts to prevent change inthe magnitude of current flowing through memory element 310 due toeither incidental or sustained contact with guide wire 314 and/or cap326 during movement of memory element 310 upon being heated above itstransition temperature.

Yet another embodiment of the invention is illustrated in FIG. 17.Reference numerals from FIGS. 15 and 16 have been applied to theassembly as shown in FIG. 17 where the same or similar parts are beingused. In this embodiment, the second lead means is different than thatshown in FIGS. 15 and 16 in that the power supply 334 andlead-attachment portion 316a are electrically coupled by means of anelectrical connection established by cap 326, guide wire 314, band 340,and lead 342.

Cap 326 includes slot 344 for receiving lead-attachment portion 316a andis made of an electrically conductive material. Preferably,lead-attachment portion 316a is welded or soldered in place in slot 344.Alternatively, a mechanical connection could be employed by deformingcap 326 about memory element 310 to clamp lead-attachment portion 316ain place. Conductive band 340 electrically communicates with proximalportion 320 of guide wire 314 and lead 342 to introduce current frompower supply 334 to conductive guide wire 314 for distribution tolead-attachment portion 316a of memory element 310. It will beappreciated that either an insulative sleeve or coating of the typesdescribed above could be employed to prevent unwanted electricalcommunication between memory element 310 and guide wire 314.

FIG. 18 illustrates rotation of guide wire 314 about its longitudinalaxis in response to heating memory element 310 above its transitiontemperature so that memory element 310 moves to assume its predeterminedshape. The solid line position B' of guide wire 314 in FIG. 18corresponds to the bent phantom line position B in FIG. 17, whilephantom line C' in FIG. 18 corresponds to solid line position C in FIG.17. Thus, in FIG. 18, the guide wire is not shown in its straightposition, but rather in each of two of its bent positions. Double arrow346 represents rotational movement of guide wire 314 relative to base324.

It has been observed that the above-described rotational movement occursduring use of each of the embodiments illustrated in FIGS. 15-17 and19-21. In particular, cap 326 moves along a path (not shown) orbitingits initial position shown in solid lines in FIGS. 15-17 and 19-21during deflection of the guide wire 314 by the heated memory element310. The guide wire 314 is coiled or otherwise configured to providemeans for converting bending forces applied to the guide wire 314 by thememory element 310 to rotation-inducing forces so that the guide wire314 rotates about its longitudinal axis in response to movement ofmemory element 310 to assume its predetermined bent shape. It hasfurther been observed that the amount of rotation is controlled by theamount of current applied.

In each of the embodiments of FIGS. 15-17, 20, and 21, the guide wire314 is configured to apply a yieldable biasing force to the memoryelement 310 upon engagement of guide wire 314 and memory element 310 sothat memory element 310 is moved to assume a shape (e.g., straight)other than its predetermined bent shape upon cooling of the memoryelement 310 to a temperature below its transition temperature.Advantageously, guide wire 314 provides yieldable means for returning acooling memory element to its initial straight position after beingheated to assume a predetermined bent position. Such a "yieldable"construction advantageously does not interfere with movement of thememory element 310 to assume its predetermined position.

Still another embodiment of the invention is illustrated in FIG. 19.Reference numerals from FIGS. 15-18 have been applied to the assembly asshown in FIG. 19 where the same or similar parts are being used. In thisembodiment, guide wire 352 is made of an electrically conductiveshape-memory alloy and is configured to provide both the "spring returnfunction" of guide wire 314 and the "deflection inducing function" ofmemory element 310.

power supply 334 is electrically coupled to cap 326 by lead 348 atjunction 350. Thus, power supply 334 can be used to vary the currentthrough the temperature-activated guide wire 352 to alter the shape ofthe guide wire 352. The spring construction of guide wire 352 will causeit to resume its initial position upon cooling to a temperature belowits transition temperature on its own volition. Advantageously, such aconstruction reduces manufacturing costs and problems.

Yet another embodiment of the invention is illustrated in FIG. 20.Reference numerals from FIGS. 15-18 have been applied to the assembly asshown in FIG. 20 where the same or similar parts are being used. In thisembodiment, memory element 310 is mounted to apply pulling forces to cap326, thereby inducing movement of guide wire 314 to assume a differentposition.

One characteristic thermal property of shape-memory alloys generally isthat such alloys exhibit a negative coefficient of thermal expansion. Inother words, shape-memory alloys contract when heated and expand, atleast under an externally applied load, when cooled. It will beappreciated that the change in length per unit of length per degreechange of temperature is practically constant for each shape-memoryalloy. Thus, one can select or design a particular shape-memory alloywhich will contract in a predetermined manner upon heating of the alloyto its transition temperature.

The embodiment illustrated in FIG. 20 is configured to exploit theabove-noted thermal expansion property of shape-memory alloys byanchoring the memory element 310 at its opposite ends 316a, b so thatmemory element 310 will apply an axial compression load to cap 326 as itcontracts under heat. Such loading will tend to pull Cap 326 and theattached distal portion 322 of Coiled spring 314 from the bent solidline position D to FIG. 20 to the straight phantom line position E alsoin FIG. 20.

In the embodiment of FIG. 20, memory element 310 is annealed to have astraight predetermined shape so that if memory element 310 is bent ortwisted while cool and then heated to its transition temperature, itwill move to regain its original straight shape. Also, guide wire 314 ispreformed to have a bent shape at its distal end, one example of whichis illustrated in FIG. 20. Thus, guide wire 314 will act to deflect thememory element 310 housed within as long as the memory element 310 iscooled below its transition temperature.

Plug means 354 is disposed in the interior chamber 312 of guide wire 314and rigidly fixed to proximal portion 320 as illustrated in FIG. 20. Itis within the scope of the present invention to insert and mount theplug 354 in guide wire 314 using a variety of techniques, including, forexample, providing a plug having external threads for threadedlyengaging a coiled spring. Of course, adhesive, soldering, welding, orthe like can be employed to provide suitable alternatives.

Plug means 354 desirably has at least an electrically conductive portionfor interconnecting lead-attachment portion 316b of memory element 310to first lead means 336 to establish an electrical path coupling memoryelement 310 and power supply 334. It will be appreciated that insulationmeans can be interposed between the electrically conductive portion ofplug means 354 and guide wire 314 to prevent electrically conductivecontact therebetween. Insulation means, for example, could comprise aseparate element, a coating, or a portion of plug means 354.

In the illustrated embodiment, first anchor means is provided, in part,by a coupling of the distal lead-attachment portion 316a to the end cap326 while a second anchor means is provided, in part, by a coupling ofthe proximal lead-attachment portion 316b to fixed plug means 354.Although memory element 310 is effectively anchored at its opposite endsto spaced-apart portions of guide wire 314, significant temperaturestresses will not develop in the memory element 310 since the memoryelement 310 enjoys sufficient freedom for expansion and contraction dueto the lengthening and shortening of resilient guide wire 314.

In operation, the bent memory element 310 shown in solid lines in FIG.20 will both straighten and contract to the phantom line position inFIG. 20 upon being heated to its transition temperature. One result ofsuch straightening is that a transverse shear load will be applied tocap 326 by the memory element 310, which load will tend to urge guidewire 314 toward its straightened phantom line position. One result ofsuch contraction is that an axial compression load will be applied tocap 326 by the double-anchored memory element 310, which load will tendto pull the distal portion 32 of the guide wire 314 toward the proximalportion 320 to assist substantially in moving the guide wire to itsstraightened phantom line position. Thus, these transverse shear loadand axial compression load cooperate to induce movement of the guidewire to its straightened phantom line position.

One advantage of this feature is that contraction of a shape-memoryalloy under heat is used to apply additional movement-inducing forces tothe distal portion 322 of guide wire 314. By generating such new forces,it is possible to decrease the size and mass of memory element 310without significantly degrading the force generation potential of such amemory element. It will be understood that it is within the scope of thepresent invention to exploit expansion/contraction of the widths orother dimensions of memory elements 310 to generate such guidewire-pulling forces of the type described above and that the inventionis not just limited to length expansion/contraction as illustrated in apreferred embodiment as shown in FIG. 20.

Still another embodiment of the invention is illustrated in FIG. 21.Reference numerals from FIGS. 15-18 and 20 have been applied to theassembly as shown in FIG. 21 where the same or similar parts are beingused. In this embodiment, a double-anchored memory element of the typeshown in FIG. 20 is directly coupled to power supply 334.

Plug means 356 is configured to accommodate a different technique formounting memory element 310 and applying a current to memory element310. Nevertheless, plug means 356 is assembled and functions in a mannersimilar to plug means 354. As shown in FIG. 21, plug means 356 is formedto include first passageway means 358 for allowing memory element 310 toextend through plug means 356 and second passageway means 360 forallowing lead 352 to extend through plug means 356.

Memory element 310 is anchored to plug means 356 using any suitableexternal and/or internal coupling means (e.g., epoxy, adhesive, weld,solder, clamp, etc.). It will be appreciated that in the case ofwelding, soldering, or the like the lead attachment portion 316b will besized and positioned relative to plug means 356 to accommodate any suchwelding or the like to the plug means 356 to preserve the shape-memorycharacteristics of shape-memory portion 318. Lead 336 is electricallycoupled to the rearwardly extending exposed end of lead-attachmentportion 316b. Lead 342 extends into interior chamber 312 and throughsecond passageway means 360 and is electrically coupled to leadattachment portion 316a adjacent to the point at which lead attachmentportion 316a is anchored to cap 326. In this embodiment, current frompower supply 334 is passed directly to memory element 310 via leads 336,242 without passing through guide wire 314.

While illustrative embodiments and uses of guide apparatus, probes, andthe like embodying the present invention have been shown and described,it will be appreciated that various modifications may be made to theillustrative embodiments without departing from the scope of the presentinvention.

What is claimed is:
 1. An apparatus comprisingan elongated tubular member having a proximal end and a flexible distal end for insertion into a body, resilient means for applying a predetermined biasing force to move the flexible distal end of the tubular member to assume a predetermined curved shape, the resilient means being coupled to the distal end of the tubular member and configured to provide the predetermined biasing force, a shape-control element coupled to the distal end, and a control mechanism configured to vary the shape of the shape-control element within the elongated tubular member so that the flexible distal end of the tubular member is moved against the biasing force provided by the resilient means to assume a shape other than its predetermined curved shape.
 2. The apparatus of claim 1, wherein the resilient means is made of a spring material preformed to define the predetermined curved shape.
 3. An apparatus comprisingan elongated tubular member having a proximal end and a flexible distal end for insertion into a body, resilient means for applying a predetermined biasing force to move the flexible distal end of the tubular member to assume a predetermined curved shape, the resilient means being coupled to the distal end of the tubular member and configured to provide the predetermined biasing force so that the flexible distal end of the tubular member is movable against the biasing force provided by the resilient means to assume a shape other than its predetermined curved shape, a core member within the distal end of the tubular member, and sleeve means for slidably coupling the resilient means to the core member so that the resilient means is permitted to slip in relation to the adjacent core member when the distal end of the tubular member is moved away from its predetermined curved shape.
 4. The apparatus of claim 3, wherein the core member is made of a resilient material preformed to define another predetermined curved shape.
 5. An apparatus comprisingan elongated tubular member having a hollow flexible tip for insertion into a body, a preformed spring coupled to the flexible tip, the preformed spring bending the hollow flexible tip to assume a predetermined curved shape, a shape-control element coupled to the flexible tip, and a control mechanism configured to vary the shape of the shape-control element within the elongated tubular member.
 6. An apparatus comprising an elongated hollow tubular member having a proximal end and a hollow flexible distal end for insertion into a body,resilient means located within said hollow tubular member for applying a predetermined biasing force to move the flexible distal end of the tubular member to assume a predetermined curved shape, the resilient means being coupled to the distal end of the hollow tubular member and configured to provide the predetermined biasing force so that the flexible distal end of the tubular member is movable against the biasing force provided by the resilient means to assume a shape other than its predetermined curved shape, and a core member within the hollow flexible distal end, the resilient means being disposed in the hollow tubular member in a space provided between the core member and the hollow flexible distal end.
 7. The apparatus of claim 6, further comprising means in said space for slidable coupling the resilient means to the core member so that the resilient means is permitted to slip in relation to the adjacent core member when the hollow flexible distal end is moved away from its predetermine curved shape.
 8. An apparatus comprisingan elongated tubular member having a proximal end and a flexible distal end for insertion into a body, resilient means having a high degree of flexibility without exceeding its elastic limit providing a predetermined bias within the distal end of the tubular member for applying a force to move the distal end of the tubular member in a first direction to assume a predetermined curved shape, the resilient means being coupled to the elongated tubular member, means for applying a steering force to selectively move the distal end of the tubular member in a second direction away from the first direction to overcome the force applied by the resilient means without exceeding the elastic limit of the resilient means so that the distal end of the tubular member is moved to assume a selected shape significantly different than its predetermined curved shape and grater than a slight bending from its predetermined shape and, wherein each resilient means returns the tubular member to the predetermined curved shape upon release of the steering force, the applying means being coupled to the elongated tubular member.
 9. An apparatus comprisingan elongated tubular member having a hollow flexible tip for insertion into a body, a preformed spring having a high degree of flexibility without exceeding its elastic limit and coupled to the hollow flexible tip, the preformed spring bending the hollow flexible tip in a first direction to assume a predetermined curved shape, means for applying a steering force to selectively move the hollow flexible tip in a second direction away from the first direction to overcome bending force applied by the preformed spring without exceeding the elastic limit of the preformed spring so that the hollow flexible tip is moved to assume a selected shape significantly different than its predetermined curved shape and grater than a slight bending from its predetermined shape, and wherein the hollow flexible tip is returned to its predetermined curved shape upon release of the steering force, the applying means being coupled tot he elongated tubular member.
 10. The apparatus of claim 9, wherein the applying means includes a shape control element of variable shape coupled to the hollow flexible tip and a control mechanism configured to vary the shape of the shape control element within the hollow flexible tip to cause the hollow flexible tip to move to assume a selected shape other than its predetermined curved shape. 